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anthonymcgrath

FEM with alembic animation cache

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hey everyone - can anyone help me with this please?  I've watched numerous tutorials on FEM online and i've gone through numerous threads on here but i'm simply having no luck.
I'm trying to get an animated character i've exported from maya into houdini and attach a FEM solution to it.  Using the follow target constraint i can attach the FEM mesh to the animated one but no matter what i try and do i just end up with a mesh either falling to the floor or (as in my attached scene) just 'hanging' off the static mesh.

I'm really lost here i've been banging my head at the wall for 2 weeks trying to suss this out.  I've followed scene files by half a dozen guys off vimeo with scene files attached but nobody seems to have a scene file i can look at that involves an animated alembic cache.

Can anyone take a look at my scene please and help me with where i've gone wrong?

thanks
anthony

hou_alembic_char_FEM_flesh_v02.zip

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SUCCESS!!!! I GOT IT WORKING !!! big_smile.png OH MY LIFE I'M SO HAPPY HAHA!

basically i was trying to drive the solid object via the high resolution mesh but the two geometries are radically different so my tet mesh (of 700 points) was just shooting up into the head area (the first 700 points in the hi res mesh!)

so i setup this…

first geometry node - CHAR_STATIC

the alembic piped through a solid embed node, then a group set on that - in my case the group was just the points of the head, body and legs - i wanted the arms to trail and drag behind. i called the group “jiggle”


second geometry node - CHAR_ANIM

similar to the first one with a solid embed. However as i scrub through the mesh kept changing topology. So i stuck a timeshift on it. I then created a pointDeform node and deformed this “frozen” mesh by the original alembic higher up in the network.

the above gave me two tetrahedralized meshes - one static & one animated but holding its tetrahedralized form.


AutoDopnetwork

now i can create the organic tissue as normal. Using the target geometry to deform it. I then created the targetConstraint node and pointed:

constrained object –> CHAR_STATIC

constrained points –> jiggle


as a noob i dont know if this is the best way to do it but it seems like i can plug any alembic mesh of a character in now and get a floppy armed goober dancing about haha

 

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well i tried animating the jiggle group node so that the char is fully constrained then a sphere scales down resulting in his limbs and torso/head becoming floppy but it doesn't seem to want to work weirdly hmmmm

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Hey Anthony,

I am having a similar problem. Might   you have a snapshot of the network so I can see? i would greatly apprecaite it. And my client is looking to see some results. :(

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6 hours ago, dreamagrery2 said:

Hey Anthony,

I am having a similar problem. Might   you have a snapshot of the network so I can see? i would greatly apprecaite it. And my client is looking to see some results. :(

I'll post up some pics and a basic scene file. Do you have some pics or can you describe what you want to do more closely? I've found a few tricks since this post you see

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Hi Anthony,

Glorious. That would be great. Basically, I am trying to have a moving mesh (alembic, obj or bgeo sequence) attached to its respective object. I want to add secondary motion onto my object. But my object is already moving. How do I combine this motion. Greatly appreciate the help.

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On 2/8/2017 at 10:07 PM, anthonymcgrath said:

I'll post up some pics and a basic scene file. Do you have some pics or can you describe what you want to do more closely? I've found a few tricks since this post you see

OP Please provide. I would love to learn how you and Erik Ferguson create these horribly realistic and disgusting fem simulations. The tests I make can't seem to get the flesh to seem "fleshy", always either overly rubbery or stiff.

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8 hours ago, Eyvus said:

OP Please provide. I would love to learn how you and Erik Ferguson create these horribly realistic and disgusting fem simulations. The tests I make can't seem to get the flesh to seem "fleshy", always either overly rubbery or stiff.


Man Erik is waaaayyyyy beyond my know how hehe!  I've literally just gone over the tutorials guys like @ParticleSkull have created on youtube and sort of expanded out from there.  I'm still learning this myself where time allows and doing some funky stuff at the moment.

If the tests seem rubbery then select your solidObject node in the dop network and under the model tab go to initialise behaviour - there's presets in there.. you can switch it to organic tissue.
If thats still not enough then you can edit the shape stiffness - figures of 0.0001 and lower (!!!) are necessary - the volume stiffness needs to down near 0.001 as well but again that all depends on your scene size.  Also look to increase the mass density too - default 976 to 1500 or heavier maybe.

start these tests on a SIMPLE object... make a platonic object, extrude its faces so you get tentacles (add subdivisions in the extrusion) then make your solid object from that... this will give you a funky organic starting shape.  add a ground plane and rotate it so the shape tumbles down a hill as such... this will tell you A LOT about how the shape is moving just using the basic simulation physics.  From there you can add in your target motion further down the line to point the thing where you want to go

Another good tip under your solidObject collisions tab turn on "collide with each component" - this will make the tentacles collide with each other!

and finally in your finite element solver you can up the quality with the substeps option and adaptive substeps and also collisons tab... so in substepping maybe set min substeps to 4 and turn on adaptive... then in collisions tab double the max collision passes - maybe more if the tentacles are intercutting through one another as it tumbles down the ground plane.

and finallest do make sure to watch particleskulls youtube vids and follow em through - they are REALLY REALLY good and get you going on it!

remember tho its a combo of effects... on top of the motion for stuff like Eriks work is some beautiful rendering with organic displacement and a macro style camera with heavy Depth of field - all this really helps amplify the overall result ;)





 

Edited by anthonymcgrath

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